Rotor and electric motor

Abstract

The present invention provides a rotor comprising: a main body composed of a soft magnetic material; and a permanent magnet provided inside or outside the main body. The permanent magnet is a bonded magnet comprising a magnet powder and a binder resin that binds the magnet powder. The bonded magnet includes 87-96 mass % of the magnet powder relative to the bonded magnet as a whole. The magnet powder includes coarse powder having an average particle diameter of 40-200 μm and fine powder having an average particle diameter of 1-10 μm. The coarse powder has a mass ratio of 60-90 mass % to a total of the coarse powder and the fine powder. The binder resin includes a thermosetting resin. The bonded magnet has a resin layer with an average thickness of 0.1-5 μm, for example, in a vicinity of a joint interface with the main body. The bonded magnet can be firmly joined to the main body, and the rotor can therefore rotate at high speed. The main body is, for example, a rotor core of an IPM motor.

1 . A rotor comprising:
 a main body composed of a soft magnetic material; and   a permanent magnet provided inside or outside the main body,   the permanent magnet being a bonded magnet comprising a magnet powder and a binder resin that binds the magnet powder,   the bonded magnet including 87-96 mass % of the magnet powder relative to the bonded magnet as a whole,   the magnet powder including coarse powder having an average particle diameter of 40-200 μm and fine powder having an average particle diameter of 1-10 μm, the coarse powder having a mass ratio of 60-90 mass % to a total of the coarse powder and the fine powder,   the binder resin including a thermosetting resin,   the bonded magnet being joined to the main body.   
     
     
         2 . The rotor according to  claim 1 , wherein the bonded magnet has a resin layer with an average thickness of 0.1-5 μm in a vicinity of a joint interface with the main body. 
     
     
         3 . The rotor according to  claim 1 , wherein the thermosetting resin is an epoxy resin. 
     
     
         4 . The rotor according to  claim 1 , wherein
 the coarse powder includes NdFEB-based magnet powder whose basic components are Nd, Fe, and B, and   the fine powder includes SmFeN-based magnet powder whose basic components are Sm, Fe, and N and/or SmCo-based magnet powder whose basic components are Sm and Co.   
     
     
         5 . The rotor according to  claim 1 , wherein the bonded magnet is formed by compression molding. 
     
     
         6 . The rotor according to  claim 1 , wherein the main body is composed of a stack of electromagnetic steel sheets. 
     
     
         7 . An electric motor comprising the rotor according to  claim 1  and a stator corresponding to the rotor. 
     
     
         8 . The electric motor according to  claim 7 , wherein the rotor is an interior magnet type in which the bonded magnet is integrally compression-molded inside the main body. 
     
     
         9 . The electric motor according to  claim 8 , wherein the rotor has a maximum rotational speed of 20,000 rpm or more.